cannwyll yr ysbryd (glân): cf. 'St Elmo's fire' yn Saesneg. Hefyd 'corposant' (< Portiwgaleg a Hen Sbaeneg 'corpo santo'' < Llad. 'corpus sanctum' neu 'corpus sancti', yn ôl yr OED.

"Those electric illuminations or phosphorescent gleams that are sometimes seen playing around the masts and rigging of ships are called by old Welsh sailors "cannwyl' [sic] yr ysbryd ("spirit candles") or "cannwyl [sic] yr ysbryd glên" (candles of the Holy Ghost) or the "Candles of St David" ...